| 摘要 |
<p>PURPOSE:To obtain an electric hot water device having high safety by calculating a plurality of temperature data obtained at different times by temperature detecting means, and controlling conduction of a heater by utilizing the result. CONSTITUTION:When control means 16 detects the conduction of a heater 8, a timer starts counting, and after a certain period ti of time is elapsed, the temperature T1 of the heater 8 is detected by temperature detecting means 15. The T1 is stored in a memory. After a certain period t2 of time is further elapsed, the means 15 detects a temperature T2. Then, a calculator calculates DELTAT=T2-T1, and a comparator compares the DELTAT with a reference value DELTAT0 input in advance. The comparator of the means 16 provides DELTAT > T0 as temporary criterion reference, and judges as abnormal dry burning if it exceeds the temperature rise, feeds a signal to a driver to stop the heater 8 through a controller 11. Thus, even if the dry burning occurs, the heater 8 can be stopped in a short period of time, thereby preventing the replacement of the heater 8 due to dry burning, ageing insulator deterioration, wire disconnection accident due to corrosion caused by the thermal deformation of the heater.</p> |
